A conventional television tube comprises a cathode ray tube of generally conical configuration. An electron gun disposed in the smaller end of the cone scans a series of horizontal lines along a phosphor film coating the viewing surface of the picture tube, exciting the phosphor and causing it to phosphoresce along each horizontal line to a degree corresponding to the intensity of the electron beam, which varies according to the video signal input.
In a typical video display the electron beam scans from left to right along the viewing screen, beginning at the top, and resets to the left-hand side of the screen for scanning successively lower horizontal lines until the entire viewing screen has been scanned. Current television video signal standards call for scanning of alternate lines in succession, to produce two fields of interlaced scanning per frame of 525 horizontal lines, at a rate of approximately 30 frames per second.
The primary disadvantage in such a video display device is the depth required to enable the electron beam to scan the viewing screen both horizontally and vertically, due to the need for each pixel on the viewing screen to be directly addressed by the electron beam and limitations on the degree to which the electron beam can be deflected. Distortion occurs along the edges of the viewing screen due to the angle of the electron beam as it approaches the outer limits of its arc. This has made the production of so-called "flat-screen" television receivers difficult.
The present invention overcomes these disadvantages by providing a thin panel video display device, in one embodiment utilizing waveguides to provide variation on the viewing screen in a single direction, for example horizontally. Each pixel is dispersed over the entire vertical length of the viewing screen, and a series of closely spaced horizontal liquid crystal lines provides vertical variation by suppressing the passage of light to the phosphor layer along all but a single horizontal line corresponding to the line scanned by the electron beam. By scanning the waveguides in sequence, and sequentially deactivating liquid crystal lines each for the duration of a single scanning cycle, both horizontal and vertical variation of the signal can be achieved even though the energy beam scans unidirectionally.
In a further embodiment a waveguide is utilized to disperse a single pixel of the video input signal over the entire area of the viewing screen, and a pair of orthogonally oriented arrays of liquid crystal lines provide horizontal and vertical variation on the viewing screen through sequential deactivation which permits the passage of light to a single pixel on the viewing screen. An imaging device utilizing this embodiment converts an image to an electrical signal which is stored in a suitable medium.